EXPRESS.JS Interview Questions & Answers - ByteScout
  • Home
  • /
  • Blog
  • /
  • EXPRESS.JS Interview Questions & Answers

EXPRESS.JS Interview Questions & Answers

EXPRESS.JS Interview Questions & Answers

1. What is Express.js?

Express.js, or Express, is a back-end web application structure for Node.js, delivered as free and open-source programming under the MIT License. It is intended for building web applications and APIs. It has been known as the de facto standard server system for Node.js.

2. What are the features of Express.js?


Express.js gives a profoundly progressed routing instrument that assists with safeguarding the condition of the website page with the assistance of their URLs.


Troubleshooting or debugging is vital for the effective advancement of web applications. Express.js makes investigating simpler by giving a troubleshooting component that can pinpoint the specific piece of the web application which has bugs.

Quicker Server-side developments:

Express.js gives numerous ordinarily utilized highlights of Node.js as capacities that can promptly be utilized anyplace in the program. This eliminates the need to code for a few hours and accordingly saves time.


Middleware is a piece of the program that approaches the information base, customer demand, and the other middlewares. It is basically liable for the methodical association of various elements of Express.js.


A template engine empowers you to utilize static layout records in your application. At runtime, the template engine replaces factors in a layout document with real qualities and changes the layout into an HTML record shipped off the customer. This methodology makes it simpler to plan an HTML page.

3. Why do you need Express.js?

  • The most important resource in any business is time. On top of that, numerous software engineers have the strain to construct productive web applications in a brief timeframe. However, coding web applications and testing them requires time. This is the place where Express.js turns into a lifeline for software engineers.
  • js can decrease the coding time significantly and still assist us in fabricating productive web applications. It diminishes the time and decreases the exertion needed to fabricate web applications with the assistance of its various highlights.
  • js is occasion-driven and can deal with a large number of customer demands simultaneously, which is absurd with PHP.
  • In this day and age, continuous web applications and administrations are expanding in notoriety. Node.js is planned solely to help genuine web applications. The most widely recognized illustration of a constant web application would be live talk. It includes a huge number of clients and continuous cooperation that can be upheld effectively by Node.js.
  • Another resource of any business is cash. It is imperative to utilize cash effectively to expand benefits. Since Express.js is an open-source and free web application that gives numerous incredible highlights, there is no explanation left not to utilize it.

4. Why should you use Express.js?

  • js upholds JavaScript, a generally utilized language that is exceptionally simple to learn and is additionally upheld all over the place. Accordingly, it will be truly simple for you to do programming utilizing Express.js if you know JavaScript.
  • With the assistance of Express.js, you can undoubtedly construct various types of web applications in a brief timeframe. Express.js gives a straightforward direction to demands made by customers. It likewise gives a middleware that is answerable for settling on choices to give the right reactions for the solicitations made by the customer.
  • Without Express.js, you need to compose your code to construct a directing segment which is a tedious and drawn-out task. Express.js offers effortlessness, adaptability, proficiency, moderation, and versatility to software engineers. It likewise enjoys the benefit of amazing execution as it is a system of Node.js.
  • js conveys every one of the executions super quick with the assistance of Event Loop that dodges any failure. The incredible presentation of Node.js and the simplicity of coding utilizing Express.js are the most mainstream highlights adored by web application engineers. Since Express.js is written in JavaScript, you can assemble sites, web applications, or even versatile applications utilizing it.

5. What are the functions of Middleware in Express.js & its types?

Middleware Functions:

  • Functions that approach the solicitation object (req).
  • The reaction object (res).
  • The following capacity in the application’s solicitation reaction cycle.

The following capacity is a capacity in the Express switch, which, when summoned, executes the Middleware succeeding the current Middleware.

Middleware can play out the tasks given below:

  • Execute any code.
  • Make changes to the solicitation and the reaction objects.
  • End the solicitation reaction cycle.
  • Call the following Middleware in the stack.

Types of Middleware:

  • Application-level Middleware
  • Built-in Middleware
  • Router-level Middleware
  • Third-party Middleware
  • Error-handling Middleware

6. What are the advantages & disadvantages of Express.js?


  • Makes Node.js web application advancement quick and simple.
  • Simple to design and modify.
  • Permits you to characterize courses of your application dependent on HTTP strategies and URLs.
  • Incorporates different middleware modules which you can use to play out extra assignments on solicitation and reaction.
  • Simple to incorporate with various format motors like Jade, Vash, EJS, and so on
  • Permits you to characterize a mistake taking care of Middleware.
  • Simple to serve static records and assets of your application.
  • Permits you to make a REST API worker.
  • Simple to interface with information bases like MongoDB, Redis, MySQL.


  • Decreases execution when taking care of Heavy Computing Tasks.
  • js welcomes plenty of code changes because of the Unstable API.
  • js Asynchronous Programming Model makes it hard to look after code.
  • Pick Wisely – Lack of Library Support can Endanger your Code.
  • Popularity with a couple of Experienced Node.js Developers.

7. What is Database integration in Express.js?

Adding the ability to associate data sets to Express applications is simply an issue of stacking a proper Node.js driver for the information base in your application.

Express.js upholds numerous RDBMS and NoSQL Databases. Adding the ability to associate data sets to Express applications is simply an issue of stacking a proper Node.js driver for the information base in your application.

Express.js upholds numerous RDBMS and NoSQL database like:

  • Prophet
  • MongoDB
  • SQLite
  • MySQL
  • PostgreSQL
  • SQL Server

8. What is Scaffolding Express.js?

Scaffolding is making the skeleton design of the application.

There are two approaches to do this:

  • Express application generator
  • Yeoman

About the Author

ByteScout Team ByteScout Team of Writers ByteScout has a team of professional writers proficient in different technical topics. We select the best writers to cover interesting and trending topics for our readers. We love developers and we hope our articles help you learn about programming and programmers.